I'll try to keep the story somewhat brief.
I've had an unplayed copy of GTA V sitting on my hard drive for like two years or something but wanted to give San Andreas another shot before starting it. People keep telling me San Andreas is one of the greatest games of all time, but when I tried it circa 2006 I found the controls unplayable and hated a lot of the core systems. After going back into it again, I actually like the game now, but the odd thing is... I like it in spite of the missions.
I'm enjoying the world and the grind of acquiring weapons and money, but the missions in my opinion kind of run counter to SA's strong suits, and there are A LOT of missions in this game. After like 20 hours I'm still only mid way trough the San Fierro missions and they're getting frustrating enough to get in the way of what I like about the game.
Is there anything else the 3rd city or the rest of the game even has to offer in terms of sandbox/grind gameplay that hasn't been introduced so far?